Method and systems for operating compressors and fan coils using electronically commutated motors

ABSTRACT

A heating, ventilation, and air conditioning (HVAC) system is described that includes a first unit and a second unit. The first unit comprises a controller configured to output a coded compressor activation signal that is based at least partially on a compressor run signal received from a thermostat. The second unit comprises at least a compressor relay. The second unit is configured to receive and decode the coded compressor activation signal from the first unit and is operable to operate the compressor relay based on the decoded content of the coded compressor activation signal.

BACKGROUND OF THE INVENTION

This invention relates generally to operation of heating, ventilation, and air conditioning (HVAC) systems, and more specifically, to operation of compressors, fan coils, and the like using electronically commutated motors (ECMs).

Energy efficiency minimum requirements continue to be tightened for HVAC equipment and systems. Therefore it has become more important that outdoor condenser/compressor units and indoor evaporator/air handler units are properly matched to one another so that it is possible to achieve the desired energy efficiency ratings.

Heretofore it has been a common practice, when servicing HVAC equipment, to retain the working unit of the indoor/outdoor pair and replace the non-working unit. In certain scenarios this practice may result in a less than optimal performance of the system, while in other cases, replacement of the non-working unit may be acceptable.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, a heating, ventilation, and air conditioning (HVAC) system is provided that includes a first unit and a second unit. The first unit comprises a controller configured to output a coded compressor activation signal that is based at least partially on a compressor run signal received from a thermostat. The second unit comprises at least a compressor relay and is configured to receive and decode the coded compressor activation signal from the first unit. The second unit is operable to operate the compressor relay based on the decoded content of the coded compressor activation signal.

In another aspect, a method for controlling operation of a compressor within a heating, ventilation, and air conditioning (HVAC) system is described. The method includes providing a compressor run signal to a first unit, utilizing the compressor run signal within the first unit to generate a coded compressor activation signal, outputting the coded compressor activation signal to a second unit that includes a compressor, and decoding the coded compressor activation signal within the second unit to determine whether the compressor is to be activated.

In still another aspect, a blower unit for a heating, ventilation, and air conditioning (HVAC) system is provided. The blower unit is configured to receive a compressor run signal from a thermostat and comprises at least one apparatus configured to generate a signal for combination with the compressor run signal. The blower unit is further configured to output a combination of the compressor run signal and generated signal as a coded compressor activation signal.

In yet another aspect, a unit for controlling operation of a compressor is provided. The unit comprises a compressor run relay and a decoder. The decoder comprises a relay coil driver operable to change a state of the compressor run relay. The decoder is configured to receive and decode a coded compressor activation signal from an external source and operable to activate the relay coil driver based on the decoded content of the coded compressor activation signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a thermostatically controlled heating, ventilation, and air conditioning (HVAC) system.

FIG. 2 is a block diagram of an indoor unit of HVAC system that incorporates a high frequency generator.

FIG. 3 is a block diagram of an indoor unit of HVAC system that incorporates a high frequency generator within an electronically commutated motor of the blower.

FIG. 4 is a block diagram of an outdoor unit of an HVAC system configured to operate with one of the indoor units of FIGS. 2 and 3.

FIG. 5 is a block diagram of an alternative embodiment of indoor unit for an HVAC system.

FIG. 6 is a block diagram of an outdoor unit of an HVAC system configured to operate with the indoor unit of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment, the methods and systems herein described prevent operation of a HVAC system where only an outdoor unit of an indoor/outdoor unit pair has been replaced. However, these same methods and systems allow operation of such HVAC systems when only the indoor unit has been replaced. Such methods and systems results in HVAC system configurations such that ever increasing efficiency enhancing measures within indoor units can be utilized though the outdoor unit may be of a different configuration.

Generally, and referring to FIG. 1, in HVAC systems 10, an indoor evaporator/air handler unit 12 contains a circuit board based controller 14 that receives a 24 volt control signal 16 from a thermostat 18. In these embodiments, circuit board controller 14 is configured such that a subset 20 of the thermostat signals are routed through to an outdoor condenser/compressor unit 22 to control the operation of a compressor, fan, and other components of outdoor unit 22. One such thermostat signal ‘Y’ is typically utilized to turn on the compressor by energizing a compressor relay 26 located within outdoor unit 22. In an alternative embodiment (not shown), a relay coil driver, operating based on a signal other than ‘Y’, may utilized to energize compressor relay 26.

FIG. 2 is a block diagram of an indoor unit 50 according to one embodiment of the present invention that is communicatively coupled to thermostat 52. Indoor unit 50 includes a controller board 51 for routing signals to and from thermostat 52 as described above. In the embodiment illustrated in FIG. 2, when a thermostat signal 54 is present that is utilized for turning on one or more of a compressor and fan within an outdoor unit, a high frequency generator circuit 56 in the indoor air handler adds a high frequency signal onto the 24 volt AC compressor run signal 58 going to the outdoor unit. Such combined signals are sometimes referred to herein as a coded compressor activation signal. High frequency generator circuit 56, in one embodiment, is additionally configured to eliminate any higher harmonics of the high frequency signal that could cause radio frequency interference by filtering and/or low duty factor operation.

In another embodiment, high frequency generator circuit 56 is configured to provide the coded compressor activation signal which can be received by an outdoor decoder board (described below). The frequency of the signal output by high frequency generator circuit 56 is chosen to be high enough, 100 KHz for example, such that the reactance found in a typical compressor relay coil will not significantly attenuate the signal, and can be easily separated from the 24 volt, 60 Hz, compressor run signal utilizing an inexpensive filter. As further described below, an absence of the high frequency signal at signal Y1, which is output to an outdoor unit, will not allow activation of the compressor associated with specific embodiments of outdoor compressor units, as further described below.

FIG. 3 is a block diagram of an alternative embodiment for an indoor unit 100. In this embodiment, a high frequency generator (not shown, but similar to high frequency generator circuit 56) is integrated into a motor control 102 of an ECM 104 that is powering a blower 106. The embodiment of FIG. 3 provides an additional operational feature to that described with respect to indoor unit 50 (shown in FIG. 2) in that ECM 104 becomes a key enabling element. Since the high frequency signal is generated within ECM 104, a possibility of tampering within indoor unit 100 to bypass the interlock provided through utilization of the high frequency compressor activation signal may be significantly reduced. Operationally however, indoor unit 100 provides the same capabilities as does indoor unit 50 (shown in FIG. 2), that is, an absence of the high frequency signal at signal Y, which is output to an outdoor unit, will not allow activation of the compressor associated with specific embodiments of outdoor compressor units, as further described below.

Indoor units 50 and 100, however, are operable with existing outdoor units, for example, those that operate compressors therein based upon receiving a 24 VAC signal from a thermostat. Though indoor units 50 and 100 impose a high frequency signal upon the 24 VAC thermostat signal, existing outdoor compressor units are capable of recognizing the 24 VAC portion of the coded compressor activation signal and controlling operation of their compressors based on whether or not the 24 VAC signal is present.

FIG. 4 is a block diagram of an outdoor unit 150 according to one embodiment of the present invention. In the embodiment, outdoor unit 150 includes a decoder circuit 152 for receiving coded compressor activation signals. Decoder circuit 152 includes a high pass filter 154, a detector 156, and a relay coil driver 158 that outputs a signal for operating compressor relay 160.

Outdoor unit 150 utilizes the high frequency coded compressor activation signals generated by either of indoor units 50 (shown in FIG. 2) and 100 (shown in FIG. 3) to determine whether to activate a compressor (not shown) by applying a signal to compressor run relay 160. More specifically, through incorporation of high pass filter 154 and detector 156, unless a high frequency signal is input into outdoor unit 150 at signal Y, relay coil driver 158 will not be enabled and the compressor will not run. The signal at Y must be of a frequency high enough to pass through high pass filter 154 and of sufficient amplitude to cause detector 156 to output a compressor activation signal.

Now referring to FIG. 5, an alternative embodiment for generating a coded compressor activation signal is illustrated. Specifically, referring to the block diagram of indoor unit 200, a control board 202 and a blower motor 204 are included. In a specific embodiment, blower motor 204 is an electronically commutated motor. In the illustrated embodiment, a compressor run signal 206 is combined with an identifying signal 208 from indoor blower motor 204 using a resistor 210. This results in a coded compressor activation signal 212 that is sent to an outdoor unit over the compressor run signal wire. In an embodiment, the indoor blower motor terminal changes its impedance in step with a changing state of identifying signal 208 so that the composite compressor activation signal 212 will be near ground potential when the output terminal of the blower motor is in a low impedance state, and at an approximately 24 VAC potential when it is in a high impedance state.

Since composite compressor activation signal 212, also labeled as Y′ in FIG. 5, cannot supply enough current to drive the compressor relay of an outdoor unit, due to the presence of resistor 210, a source of 24 VAC is needed in any outdoor unit that is utilized with indoor unit 200. In one embodiment, the ECM operating as the blower motor is configured with an open collector output channel, which is utilized to provide identifying signal 208. In various embodiments, identifying signal 208 can consist of a frequency code or a pulse code that is received by the decoder board in the outdoor unit. This output channel is configured in a specific embodiment so that indoor unit can provide identifying signal 208 only during a positive portion of the AC signal from control board 202, as the ECM incorporates a diode that clamps the negative portion of the AC signal.

FIG. 6 is a block diagram for an outdoor unit 250 that is operable with the indoor unit 200 of FIG. 5. Specifically, outdoor unit 250 includes a decoder board 252 that includes a transient filter 254 receiving composite signal 212 from indoor unit 200. Decoder board 252 also includes a processing unit (microcontroller 256) that receives signals through transient filter 254 and controls operation of relay coil driver 258. Relay coil driver 258, in conjunction with a DC bias power supply 260 and a 24 VAC supply 262, control operation of compressor run relay 264, thereby controlling operation of a compressor (not shown).

In one embodiment, the components of decoder board 252 evaluate the signal on Y′ for the presence of a combined compressor run signal and identifying signal from the ECM motor 204 (shown in FIG. 5). In this embodiment, decoder board 252, through filter 254 and processor 256, are able to discriminate between a positive voltage containing both the blower identifying signal and a half wave DC signal (the compressor run signal) or no signal. If the compressor run signal is present with or without the blower identifying signal, compressor relay 264 will be energized. If a preset time elapses without processor 256 detecting the identifying signal, compressor relay 264 will be deenergized and locked out for a predetermined time. Otherwise the compressor (and condenser fan) will be allowed to run.

As described above, if a standard outdoor unit (i.e., not one of the above described embodiments) is to be connected to one of the above described indoor units, the compressor activation signal has to be connected to the same terminal as the compressor signal thermostat, so that the outdoor unit is provided with a typical 24 VAC run signal for activating the compressor, though the 24 VAC signal may be combined with a high frequency signal or other frequency coded or pulse coded signal.

If an outdoor unit is utilized that is configured to be paired with one of the above described indoor unit, it will contain a decoder circuit (see outdoor unit 250 shown in FIG. 6) or filter circuit (see outdoor unit 150 shown in FIG. 4). The output of the decoder or filter is connected to the input of a relay driver circuit, which in turn switches the 24 volt AC to the compressor relay coil (158 or 258). Such a configuration makes an outdoor unit unresponsive to a typical 24 VAC, 60 Hz, control signal, but responsive to the frequency or coded signal received from one of the above described indoor units.

If one of the above described outdoor units 150 or 250 is connected to an indoor unit that does not have the identifying, or high frequency, signal, the compressor will be prevented from operating since a typical 24 VAC, 60 Hz, compressor run signal will not satisfy the conditions needed to pass the compressor activation signal through decoder board 252 or the combination of filter 154 and detector 156.

As described above, the methods and systems prevents the operation of an outdoor condenser/compressor unit with an indoor fan coil unit that is not configured to operate with the indoor fan coil unit, while allowing the operation of other outdoor unit/indoor unit combination. Such configurations allow an HVAC system that may include one or more replacement components to comply with increasingly rigid energy efficiency ratings while providing the performance desired by users of such HVAC systems.

Additionally, two stage compressor systems within outdoor units are becoming popular because of the higher efficiency attainable when they run at a lower capacity stage. The methods and systems described herein are easily extensible to such two stage compressor systems, for example, utilizing two different high frequency signals for selection of the two compressor stages in combination with one or more of a separate relay and driver signal for each stage and a single relay utilized in conjunction with a switching circuit to provide either of a first stage connection and a second stage connection to the compressor.

While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims. 

1. A heating, ventilation, and air conditioning system comprising: a first unit comprising a controller configured to output a coded compressor activation signal, the coded compressor signal based at least partially on a compressor run signal received from a thermostat; and a second unit comprising at least a compressor relay, said second unit configured to receive and decode the coded compressor activation signal from said first unit, said second unit operable to operate said compressor relay based on the decoded content of the coded compressor activation signal.
 2. A heating, ventilation, and air conditioning system according to claim 1 wherein said first unit comprises a high frequency generator arid said second unit comprises a high pass filter and a detector receiving an output of said high pass filter, said first unit configured to combine a compressor run signal received from a thermostat with the high frequency for output as the coded compressor activation signal.
 3. A heating, ventilation, and air conditioning system according to claim 2 wherein said first unit comprises a blower motor, said high frequency generator integrated into a controller of said blower motor.
 4. A heating, ventilation, and air conditioning system according to claim 3 wherein said blower motor comprises an electronically commutated motor.
 5. A heating, ventilation, and air conditioning system according to claim 2 wherein said second unit comprises a compressor relay, an output of said detector operable to control operation of said compressor relay.
 6. A heating, ventilation, and air conditioning system according to claim 1 wherein said first unit comprises a blower motor, and wherein to provide a coded compressor activation signal, said first unit configured to combine a compressor run signal received from a thermostat with an identifying signal output by said blower motor.
 7. A heating, ventilation, and air conditioning system according to claim 6 wherein the compressor run signal and the identifying signal are combined using a resistor.
 8. A heating, ventilation, and air conditioning system according to claim 7 wherein the compressor activation signal is near ground potential when the output of said blower motor in a low impedance state and at an approximate 24 VAC potential when the output of said blower motor is in a high impedance state.
 9. A heating, ventilation, and air conditioning system according to claim 1 wherein said second unit comprising at least a plurality of compressor relays, each said relay operable to for activating a different stage of a compressor, said second unit configured to receive and decode the coded compressor activation signal from said first unit, said second unit operable to activate an appropriate one of said compressor relays based on the decoded content of the coded compressor activation signal.
 10. A method for controlling operation of a compressor within a heating, ventilation, and air conditioning system, said method comprising: providing a compressor run signal to a first unit; utilizing the compressor run signal within the first unit to generate a coded compressor activation signal; outputting the coded compressor activation signal to a second unit that includes a compressor; and decoding the coded compressor activation signal within the second unit to determine whether the compressor is to be activated.
 11. A method according to claim 10 providing a compressor run signal to a first unit comprises utilizing a thermostat to output a compressor run signal.
 12. A method according to claim 10 wherein utilizing the compressor run signal within the first unit to generate a coded compressor activation signal comprises combining the compressor run signal with a high frequency signal for output as the coded compressor activation signal.
 13. A method according to claim 12 further comprising integrating a high frequency generator into a controller of a blower motor within the first unit.
 14. A method according to claim 12 wherein decoding the coded compressor activation signal within the second unit comprises: high pass filtering the coded compressor activation signal; applying a result of the high pass filtering to a detector; and controlling operation of the compressor based on an output of the detector.
 15. A method according to claim 10 wherein utilizing the compressor run signal within the first unit to generate a coded compressor activation signal comprises combining a compressor run signal received from a thermostat with an identifying signal output by a blower motor within the first unit.
 16. A method according to claim 15 wherein combining the compressor run signal with an identifying signal output comprises combining the compressor run signal and the identifying signal utilizing a resistor.
 17. A method according to claim 15 wherein combining the compressor run signal with an identifying signal output comprises: outputting a coded compressor activation signal at an approximate ground potential when the identifying signal is in a low impedance state; and outputting a coded compressor activation signal at an approximate 24 VAC potential when the identifying signal is in a high impedance state.
 18. A method according to claim 17 wherein decoding the coded compressor activation signal further comprises activating the compressor based on a state of the coded compressor activation signal.
 19. A method according to claim 10 wherein said decoding the coded compressor activation signal within the second unit to determine whether the compressor is to be activated comprises decoding the coded compressor activation signal to determine which compressor stage should be activated.
 20. A blower unit for a heating, ventilation, and air conditioning system, said blower unit configured to receive a compressor run signal from a thermostat and comprising at least one apparatus configured to generate a signal for combination with the compressor run signal, said blower unit further configured to output a combination of the compressor run signal and generated signal as a coded compressor activation signal.
 21. A blower unit according to claim 20 wherein said at least one apparatus comprises a high frequency signal generator, said blower unit configured to combine the output of said high frequency signal generator with the compressor run signal.
 22. A blower unit according to claim 21 further comprising an electronically commutated motor comprising a motor controller, said motor controller configured with said high frequency signal generator.
 23. A blower unit according to claim 20 further comprising a blower motor, said at least one apparatus configured to combine the compressor run signal with an identifying signal output by said blower motor.
 24. A blower unit according to claim 23 wherein said at least one apparatus is configured to: output a coded compressor activation signal at an approximate ground potential when the identifying signal is in a low impedance state; and output a coded compressor activation signal at an approximate 24 VAC potential when the identifying signal is in a high impedance state.
 25. A blower unit according to claim 20 wherein the coded compressor signal comprises information regarding which stage of a compressor is to be activated.
 26. A unit for controlling operation of a compressor, said unit comprising: a compressor run relay; and a decoder, said decoder comprising a relay coil driver operable to change a state of said compressor run relay, said decoder configured to receive and decode a coded compressor activation signal from an external source, said decoder operable to activate said relay coil driver based on the decoded content of the coded compressor activation signal.
 27. A unit according to claim 26 wherein said decoder comprises: a high pass filter; and a detector, said high pass filter configured to receive the coded compressor activation signal and output a signal to said detector, said detector operable to activate said relay coil driver based on an amplitude of the signal received from said high pass filter.
 28. A unit according to claim 25 wherein said decoder comprises: a high pass filter; and a detector, said unit comprising a plurality of compressor run relays each configured for activating a single stage of a compressor, said decoder comprising a respective plurality of relay coil drivers, said detector operable to activate a specific said relay coil driver based on the decoded content of the coded compressor activation signal. 